Method of mining subterranean rubble piles

ABSTRACT

A method is described for setting a liner in a rubble pile located on the floor of a subterranean cavity which is being solution mined. The invention involves the placing of a liner in a rubble pile on a subterranean cavity floor by introducing the liner with the drilling string. The liner is carried to the bottom of a subterranean cavity and inserted in the rubble pile located on the cavity floor by thrust bearings positioned on the tubing string and spaced apart from each other a distance greater than the distance encountered by the liner associated with the drilling string. Provision is made for insertion of the liner into the rubble pile once the drill has entered the pile a desired distance and means are provided for cutting the drill bit from the assembly. Specific provisions are made in the liner assembly for the introduction of fluid to the rubble pile and the removal of fluid therefrom.

' United States Patent 2,745,647 5/1956 Gilmore inventor Selby W. Porter Calgary, Alberta, Canada Appl. No. 049,894

Filed June 25, 1970 Patented Aug. 17, 1971 v Assignee Kalium Chemicals Limited Regina, Saskatchewan, Canada Continuation-impart of application Ser. No. 790,581, Jan. 13, 1969, now abandoned METHOD OF MINING SUBTERRANEAN RUBBLE PlLES 8 Claims, 2 Drawing Figs.

US. Cl

2,822,158 2/l958 Brinton ABSTRACT: A method is described for setting a liner in a rubble pile located on the floor of a subterranean cavity which is being solution mined. The invention involves the placing of a liner in a rubble pile on a subterranean cavity floor by introducing the liner with the drilling string. The liner is carried to the bottom of a subterranean cavity and inserted in the rubble pile located on the cavity floor by thrust bearings positioned on the tubing string and spaced apart from each other a distance greater than the distance encountered by the liner associated with the drilling string. Provision is made for insertion of the liner into the rubble pile once the drill has entered the pile a desired distance and means are provided for cutting the drill bit from the assembly. Specific provisions are made in the liner assembly for the introduction of fluid to the rubble pile and the removal of fluid therefrom.

PATENTEU nus] nan 3,500,039

sum 1 BF 2 I k SELBY W- v PORTER/ PATENTED mm 7 I971 SHEET 2- BF 2 INVENTOR Sam M Paxrn P4, A RNEYS BACKGROUND OF THE INVENTION I This application is a continuation-in-part application of applicants waste application Ser. No. 790,581, filed .I an. 13, 1969 and now abandoned.

The solution mining of subterranean deposits of minerals such as sodium chloride, potassium chloride, magnesium chloride and mixed deposits of these and other salts which can be solubilized with suitable solvents usually involves the ex cavation of large subterranean cavities in the mineral deposit in which the desired salts are located. During the course of the development of these cavities, a rotating of which expand in lateral directions to distances of 50 feet or more, quite frequently 300 to 400 feet in length, present some problems in that roof collapse frequently occurs. When the roof of a subterranean cavity does collapse, large rubble piles are normally formed on the floor of the cavity. These rubble piles, in addition to containing insoluble materials, frequently contains large quantities of soluble salts. These soluble products, because they are buried in large rubble piles containing insolubles as well, are not easily mineable. It is therefore desirable to insert a liner assembly in such rubble piles for the purpose of introducing solution to the salts located in the rubble piles and in this manner dissolved the mineral content thereof. Since these deposits are located typically 2 to 7,000 feet or more below the surface of the ground, it is extremely difficult to drill a hole in a rubble pile and then set a liner in it since the drill hole in such a pile presents an extremely small target for a liner introduced through a cased borehole from the surface of the ground. Thusa great deal of time and effort is involved in attempting toset liners into holes drilled inrubble piles on cavity floors due to the fact a very small target area is presented.

THE INVENTION In accordance with the instant invention a liner suitable for solution mining the mineral content of a rubble pile located on a subterranean cavity floor is carried down on thrush bearings located on a drilling string. The thrust bearings are so placed and-spaced apart from each other on the drill string that there is no thrust load applied to the liner associated with the drill string. Providing a liner on a drill string in this manner it is possible to drill into a rubble pile located on a cavity floor with the liner in place on the drilling string and located a given distance above the drill bit. Once the drill bit has entered the rubble pile and traversed it a substantial distance to reach what has been determined to bethe cavity floor, the drill bit may cut loose and the liner left standing in the borehole created by the drilling operation. In this manner the liner is set readily in the borehole established in the rubble pile and solution mining of the mineral content of the rubble pile can take place without the necessity of trying to locate a drilled hole therein. It is an important consideration in practicing the method of the instant invention that the linerassembly be spaced between thrust bearings which are located in their spaced relationship to each other a distance apart from each other substantially larger than the distance occupied by the liner itself. Thus on a tubing string where a liner is positioned for the purpose of drilling into a rubble pile on a cavity floor with the liner in place, it is necessary that the thrust bearings which are utilized to carry the liner into the rubble pile be spaced apart from each other a distance at least 2 percent greater than the distance of the longitudinal dimension of the liner which is positioned between the bearings. Operating in this fashion the liner in its traversal through the rubble and the subterranean cavities associated therewith will remain straight and not bend unduly. The tubing string which is normally subject to some compression and bending during drilling is conlined in its bends and distortions during drilling by the confines of the liner associated therewith. Once in place, the liner of the instant invention can be used with normal or reversed circulation of solution in a solution mining cavity without detracting from its usefulness.

For a more complete understanding of the instant invention reference is made to the accompanying drawings in which:

FIG. 1 is a diagrammatic illustration of the drill down liner of theinstant invention positioned on a tubing string with a drill bit attached boring into a rubble pile located on the bottom of a solution mining cavity.

FIG. 2 is a diagrammatic illustration of the-drill'down liner of F IG. 1 where the drilling has been completeda'rid the unit is ready for cutting to set'the liner in the rubble pile for solution mining.

Turning to FIG. 1 there is shown drill pipe or string I carrying a bit member 2 at the lower extremity thereof positioned in a cased borehole 3. The tubing string 1 to which the bit 2 is attached has a drilling string section 4 having affixed to it a protector plate 5. This plate 5 is positioned above a tapered roller bearing member 6. A stop ring 7 is provided below the roller bearing member 6. A bearing race member 8 is attached to the liner 9 also positioned on the drill string section 4. A coupling member 23 is shown on the drill string section 4. It will be understood that a multiplicity of such couplings may be employed depending on the number of pipe sections used in any given length of drill strings. Packer cups l1 and 12 are provided on the liner 9 for use in sealing the liner 9 to the casing 3. Holes or apertures indicated at 13 are provided through the liner at points placed above the packer cups 11 and 12. These holes permit communication between the interior of the liner member 9 and the space 15 provided between the exterior liner wall and the inside wall of the casing member 3. A further setof holes 14 is provided at the lower end of the liner member 9. These holes or apertures 14 communicate with the interior of the liner 9 and permit fluid flow into the liner annular space 25 provided by the interior wall of the liner 9 and the exterior or outside wall of the drilling string member 4. Another coupling member 16 is located at the bottom of the drilling string section 4. A stop ring member 17 is located at the bottom portion of the drilling string section 4 and is attached to and abuts a second tapered roller bearing member 18 which in turn abuts a protector plate 19. The cavity is generally indicated by 20 and a rubble pile located on the bottom of it is generally indicated as 21. A coupling member 22 is shown on the liner 9 and permits the positioning of additional sections of liner on the drilling string 4. Member 24 is a coupling member for adding more sections to the drill string 1. Bit 2 is a conventional rock drilling bit. A hearing race 25 is attached to the bottom of liner 9 and engages the tapered roller bearing 18, thereby supporting the weight of the liner being carried down on the drill string.

In the operation of the device in accordance with FIG. 1, the tubing string 1 is assembled above ground and provided with the liner member 9 having the configurations and associated parts as set forth in FIG. 1. The tubing string is introduced into the subterranean cavity 20 and drilling of the rubble pile formation 21 located at the base of the cavity 20 is begun. Drilling is continued until the drill bit 2 reaches the floor of the cavity. This location may be determined by conventional logging techniques known in the art. Thus the floor of the cavity can be determined by wire line methods of locating cavity bottoms and will essentially be located at the depth at which the solution mining was begun when the cavity 20 was first developed. When the drill bit has reached desired depth in the rubble pile 21 located on the floor cavity 20, the drilling operation is suspended. If it is desired that the drill string be removed from the hole, a wire line method or mechanical cutter may be used to cut the bit free and the liner assembly 9 will then be left in the rubble pile as a free standing unit with the bit falling to the bottom of the hole.

During the drilling operation itself the positioning of the thrust bearings 6 and 8 is such that the spacing between the bearing is at least 2 percent greater than the length of the liner which is interposed between the bearings. Preferably this spacing or distance between the bearings is between 2 to 10 percent greater than the length of the liner employed. Providing a spacing of the bearings in this manner insures that no thrust load is applied to the liner by the drill string during the drilling operation. Without this thrust load applied to the liner by virtue of this arrangement of the bearing spacing, the tendency of the liner to bend during drilling is greatly minimized or completely avoided.

The invention is particularly useful in those instances where more than one solution mining cavity are in existence and it is desired to introduce solvent into one cavity and remove it from adjacent cavity. Thus a large cavity can exist in a subterranean mineral deposit in which a large rubble pile has been formed at the base of the cavity and the cavity has been connected to a second cavity through the utilization of fracturing techniques and other similar solution mining expedients. In these instances solvent is typically introduced into one cavity and the solution containing the dissolved minerals is removed from the second cavity to provide sufficient residence time for maximum solubilization of mineral salts. Where a substantial rubble pile has formed in a cavity which has been extensively mined, the drill down lining system of the instant invention can be employed, the liner set in the rubble pile on the floor of the cavity containing the rubble pile and solution then introduced through the liner member to the rubble pile and removed from a second cavity. Obviously the invention has particular utilization where a single cavity is being employed and it is desired to merely dissolve minerals located within a rubble pile. In this instance of course the liner member 9 is set in the rubble pile and solution is introduced through the liner member 9 to the walls of the rubble pile and the dissolved mineral salts from the rubble pile are brought out of the cavity by passage up through the liner member.

The drill down liner assembly of the instant invention as shown in FIGS. 1 and 2 was employed to drill a hole into the rubble pile and set the liner member 9 therein. The drilling string'had a liner member 9 150 feet in length. The thrust bearings were spaced apart from each other a distance of 153 feet. Solvent was introduced into the liner member after it was set in the rubble pile by introducing solvent down through the drill string member 1. Return solution containing dissolved minerals was removed through lines 14, annulus 25, lines 13 and annulus 15 to the surface of the ground for recovery of mineral deposits. Satisfactory solubilization of the mineral deposits contained in the rubble pile was readily achieved.

This apparatus and method is of course useful in mining various salts such as NaCl, KCI, MgCl,, limestone and mixed salts beds. Solvents suitable for the dissolution of these materials include water, brines, acid solutions such as hydrochloric acid for limestone mining and other similar solvents for the specific salts to be mined. ln mining mixed deposits of KCl-NaCl for example, water or brines rich in NaCl and lean in KCI or brine weak in both NaCl and KCI content can be used effectively.

Thus, while particular apparatus and methods have been described with reference to the specific embodiments herein described, it is of course to be understood that the invention is not to be limited thereby except insofar as appears in the accompanying claims.

I claim:

1. A method of solution mining the mineral content of a rubble pile positioned on the floor of a subterranean cavity comprising introducing into a borehole communicating with said cavity a drilling string having a drill bit positioned on the lower end and a liner surrounding at least a part of said drilling string, providing a thrust bearing at the lower end of said liner and a second thrust bearing positioned on the drill string above said liner, the thrust bearings being maintained spaced from each other a distance greater than the length of said liner, drilling into said rubble pile with the drilling string and liner until the drill bit has reached a predetermined depth introducing solvent into the drill string and removing dissolved minerals throu hsaid liner.

2. A metho of solution mining the mineral content of a rubble pile positioned on the floor of a subterranean cavity comprising introducing into a borehole communicating with said cavity a drilling string having a drill bit positioned on the lower end and a liner surrounding at least a part of said drilling string, providing a thrust bearing at the lower end of said liner and a second thrust bearing positioned on the drill string above said liner, the thrust bearings being maintained spaced from each other a distance at least about 2 percent greater than the length of said liner, drilling into said rubble pile with the drilling string and liner until the drill bit has reached a predetermined depth introducing solvent into the drill string and removing dissolved minerals through said liner.

3. The method of claim 1 wherein said bearings are maintained spaced from each other a distance of between 2 to about 10 percent greater than the length of the liner. and inwardly 4. A method of solution mining a rubble pile located on the floor of a subterranean cavity comprising introducing into a cased borehole a drill disposed having positioned thereon a liner, drilling into the rubble pile with a bit on the end of said drill string while applying the weight of the liner to the drill string through a thrust bearing positioned between the bit and the liner, restricting the lateral movement of the drill string during drilling by providing a second thrust bearing on the drill string and above the liner, drilling to a predetermined level in said rubble pile, sealing the liner against the casing wall, introducing solvent through said drill string and into said rubble pile and removing dissolved minerals through said liner and the casing above the liner.

5. The method of claim 4 wherein the distance between said bearings is between about 2 to about 10 percent greater than the length of the liner.

6. A method of solution mining the mineral content of a rubble pile positioned on the floor of a subterranean cavity comprising, introducing into a bore hole communicating with the cavity a tubing string having a drill bit positioned on the lower end thereof and a liner assembly associated with the tubing string, maintaining the weight of the liner on the drill bit during drilling, restricting any substantial bending of the tubing string during drilling, and drilling into a rubble pile with the tubing string and associated liner until the drill bit has reached a predetermined depth, introducing solvent into the rubble pile and removing dissolved minerals therefrom.

7. The method of claim 6 wherein the tubing string is prevented from any substantial bending by limiting the vertical movement of the associated liner.

8. The method of claim 6 wherein the rubble pile is positioned on the floor of a cavity in communication with a second cavity and wherein solvent is introduced to the pile through said liner and dissolved minerals are removed from the second cavity.

@3 3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patentlkn 3,600,039 Dated Auqust l7 1971 Inventor(s) S lbv W, Porter It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 26, after the period(.) cancel "and in-;

line 27, cancel "wardly"; line 30, cancel "disposed" and insert--string--.

Signed and sealed this 7th day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Commissioner of Patents Attesting Officer 

1. A method of solution mining the mineral content of a rubble pile positioned on the floor of a subterranean cavity comprising introducing into a borehole communicating with said cavity a drilling string having a drill bit positioned on the lower end and a liner surrounding at least a part of said drilling string, providing a thrust bearing at the lower end of said liner and a second thrust bearing positioned on the drill string above said liner, the thrust bearings being maintained spaced from each other a distance greater than the length of said liner, drilling into said rubble pile with the drilling string and liner until the drill bit has reached a predetermined depth introducing solvent into the drill string and removing dissolved minerals through said liner.
 2. A method of solution mining the mineral content of a rubble pile positioned on the floor of a subterranean cavity comprising introducing into a borehole communicating with said cavity a drilling string having a drill bit positioned on the lower end and a liner surrounding at least a part of said drilling string, providing a thrust bearing at the lower end of said liner and a second thrust bearing positioned on the drill string above said liner, the thrust bearings being maintained spaced from each other a distance at least about 2 percent greater than the length of said liner, drilling into said rubble pile with the drilling string and liner until the drill bit has reached a predetermined depth introducing solvent into the drill string and removing dissolved minerals through said liner.
 3. The method of claim 1 wherein said bearings are maintained spaced from each other a distance of between 2 to about 10 percent greater than the length of the liner. and inwardly
 4. A method of solution mining a rubble pile located on the floor of a subterranean cavity comprising introducing into a cased borehole a drill disposed having positioned thereon a liner, drilling into the rubble pile with a bit on the end of said drill string while applying the weight of the liner to the drill string through a thrust bearing positioned between the bit and the liner, restricting the lateral movement of the drill string during drilling by providing a second thrust bearing on the drill string and above the liner, drilling to a predetermined level in said rubble pile, sealing the liner against the casing wall, introducing solvent through said drill string and into said rubble pile and removing dissolved minerals through said liner and the casing above the liner.
 5. The method of claim 4 wherein the distance between said bearings is between about 2 to about 10 percent greater than the length of the liner.
 6. A method of solution mining the mineral content of a rubble pile positioned on the floor of a subterranean cavity comprising, introducing into a bore hole communicating with the cavity a tubing string having a drill bit positioned on the lower end thereof and a liner assembly associated with the tubing string, maintaining the weight of the liner on the drill bit during drilling, restricting any substantial bending of the tubing string during drilling, and drilling into a rubble pile with the tubing string and associated liner until the drill bit has reached a predetermined depth, introducing solvent into the rubble pile and removing dissolved minerals therefrom.
 7. The method of claim 6 wherein the tubing string is prevented from any substantial bending by limiting the vertical movement of the associated liner.
 8. The method of claim 6 wherein the rubble pile is positioned on the floor of a cavity in communication with a second cavity and wherein solvent is introduced to the pile through said liner and dissolved minerals are removed from the second cavity. 